Transactions of the Medical Society of King's College, London.

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Credit: Transactions of the Medical Society of King's College, London. Source: Wellcome Collection.

    113/262 (page 103)
    breathing animals; no fishes having the power of producing any vocal sound. In reptiles, the vocal apparatus exists in a very rudimentary form ; the sound is generated at the top of the trachea where it opens into the pharynx by a mere slit, bounded by two contractile lips. In birds the organ of voice is situate at the bifurcation of the trachea, while a second larynx, resembling that of reptiles, at the top of the trachea, regulates the ingress and egress of air. In mammalia there is but one larynx, which serves the double purpose of regulating respiration and generating sound ; in most animals this organ bears a very close resemblance to the human larynx. The power of articulation, which is only found in man, does not depend so much on his physical as on his mental endowments, since many animals are capable of being taught to utter articulate sounds, though incapable of more than a very general apprehension of their import. Almost all animals of the mammalian class have the power of genera¬ ting some vocal sounds; there are, however, one or two ex¬ ceptions, as the giraffe, armadillo, &c. It is scarcely necessary for me to prove that the larynx is the principal organ of voice in man; it is shown conclusively by the following facts : sounds resembling the human voice can be produced in a larynx removed from the body; when the larynx of a living animal is exposed, it is seen to be in action when a sound is produced; in a case which fell under the observation of Mr. Mayo, a man in an attempt to commit suicide, had cut off the upper part of the thyroid cartilage and exposed the vocal cords; the larynx was seen to be in action during vocalisation. When an opening is made in the trachea, so that no air passes through the larynx, no sound is generated ; when the opening is closed, so that air again passes through the larynx, sound will be reproduced. The